Control mechanism for brake holders



y 5, 1953 G. A. GUERNSEY ET AL 2,637,416

CONTROL MECHANISM FOR BRAKE HOLDERS Filed March 15, 1951 MPH. o a 6 .9 a /5 /a 2/ 242730 33 IRE/7.0 50 no 200 300 400 500 ATTORNEYS Patented May 5, 1953 UNITED STATES PATENT OFFICE CONTROL MECHANISM FOR BRAKE HOLDER S Application March 15, 1951, Serial No. 215,845

3 Claims. 1 This invention relates to improvements in control mechanism for the brake holders of automotive vehicles.

' Brake holders are particularly useful in automotive vehicles of the type, in which the power of the motor is transmitted through a fluid coupling to the propeller shaft and driving wheels of the vehicle, for the purpose of automatically holding the vehicle stationary, after it has been brought to a stop, without requiring the operator to maintain pressure on the brake pedal. In a hydraulic braking system, the brake holder commonly consists of a valve, which is interposed in the conduit between the master cylinder and the brake cylinders of certain wheels of the vehicles and which, when closed, prevents the return of brake fluid from such cylinders and thus holds applied the brakes of the selected wheels. When this valve closes, fluid under pressure is trapped in the conduit between the valve and the selected L brake cylinders, the amount of the pressure varying according to the force with which the operator applies the brake pedal. Various means have heretofore been proposed for causing the brakeholding valve to automatically close after the brakes have been applied and the speed of the vehicle been reduced to a predetermined low value. However, the application of the brake holder invariably at a predetermined low speed does not produce uniformly good results. Much depends on the way the operator brings the vehicle to a stop. A heavy pressure on the brake pedal, that is maintained until the selected predetermined low speed is reached, will result in a lurching stop because the brake-holding valve, closing at this low speed, will trap fluid under high pressure in the brake cylinders and the vehicle will be brought to a sudden stop. Since the brake-holding valve closes at the predetermined low speed and remains closed until the vehicle is subsequently accelerated, the control is taken away from'the operator and he will not be able to reduce the braking pressure by relaxing his foot pressure on the brake pedal, as he might wish to do in order to secure a smooth'stop. On the other hand, if the operator applies the brakes more gradually, using less pressure applied over a greater time, the brake-holding valve may be closed at the predetermined low speed and result in a smooth stop because much less pressure will be trapped in the brake cylinders when the valve closes.

This invention has for an object the provision of an improved brake holder control, which overcomes the' disadvantages aforesaid and which is characterized in that the brake holder is automatically applied after a certain time delay,

starting from the time when the speed of the propeller shaft decreases to a certain low value. While the extent of this time delay is variable, it may for example be approximately the time needed to decelerate the propeller shaft at a normal rate from the certain low speed to zero. Then, if the vehicle is decelerated at a higher rate, the brake holder will not be applied until after the vehicle has stopped, and if the vehicle is decelerated. at a rate that is slower than normal, the brake holder will be applied before the propeller shaft has entirely stopped.

The invention has for an object the provision in a brake holder control system, of actuating means for the brake holder, such means including a member having a relatively high coefficient of expansion and operable, when expanded to a predetermined extent, to apply the brake holder and maintain it applied, a means for heating the member, and means for controlling the heating means responsive to the speed of the propeller shaft of the vehicle and initiating effective heating of such member at relatively low propeller shaft speeds corresponding to vehicle speeds of a few miles per hour.

The invention has for an object the provision in a brake holder control system of an improved time delay means for closing the starting switch in the energizing circuit of the electrical means that actuates the brake holder, such time delay means consisting of a member which has a high coefficient of expansion and is operable by its contraction and expansion to control the opening and closing of the switch, together with means responsive to the speed of the propeller shaft of the vehicle for controlling the heating of said member and initiating the effective heating of such member at a predetermined propeller shaft speed corresponding to a vehicle speed of a few miles per hour and maintaining effective heating of such member at speeds below said predetermined speed.

The invention has for a further object the provision of a time delay switch in the energizing circuit of the actuating means for the brake holder, such switch including a resistance wire holding the contacts of the switch separated against the force of a spring tending to engage the contacts, and means responsive to the speed of the propeller shaft of the vehicle for controlling the heating of such wire and initiating effective heating of the wire at relatively low propeller shaft speeds corresponding to vehicle speeds of only a few miles per hour.

These and other objects will best be understood from the detailed description of one illustrative Fig. 3 is an electrical diagram of the control system of the brake-holding .means; and

Fig. 4 is a graph illustrative .of :theoperatio-n of the voltage varying means.

In Fig. 1, there has been shown iii-diagrammatical form those parts of .a motor-driven wheeled vehicle that need to be considered for an understanding of the present invention. There are shown the motor i; carburetor 2; throttle valve .3; an accelerator pedal l, operable when depressed to open valve 3 through suitable connections, such as rod 5,.lever 5, rod 1 and lever 8; hydraulic clutch'll; transmission-l; propeller shaft ll; wheels i2, the rear ones of which are driven from shaft H in the usual way; brake drums 13 on wheels '12 brake shoes Id in each drum; brake cylinders 55 one within each drum for actuating'the brake shoes by hydraulic pressure; a brake pedal IE; and a master cylinder I'Lhaving therein the usual piston (not shown), which is connected, as by r031 iii, to pedal ii to be actuated by thelatter, when depressed, and transmit pressure through conduits Iii to the brake cylinders onthe rear wheels and through conduits to the brake cylinders on the front wheels.

The brake holder is indicated generally at 2! in Fig. 1. It includes a normally open valve of any suitable kind adapted to be interposed in the conduit between the master cylinder I1 and those brake cylinders I5, which it is desh ed to control. In this case, the brake holder'is interposed in the conduit '28 leading only to the brake cylinders of the front wheels, which-is deemed preferable although, as is well known in the art, the brake holder may also be made to control only the brakes or the rear wheels'or the brakes of all the wheels. An illustrative example of one valve unit, suitable for the p-urposais shown in Fig. 2. The casing 2! has slidaoly mounted therein a valve 22 for controlling the communication between inlet and ou'tlet passages 23 and 24, respectively connected on the master cylinder. side and brake cylinder side to the conduit 29. Thestem of valve 22 is in part a magnetic plunger 25 cooperating with a solenoid 26. A spring 2? tends to hold the valveopen. This solenoid, when energized sufficiently, will close valve'22 against the pressure of spring 2'1. Brake holders of .this general type, for the purpose described, are old and well known in the art.

The present invention has to do with the control of the brake holder and particularly'with the automatic'application of it,by a'simplified and improved time-delaymeans, the actionof which is initiated by means responsive to the speed of the propeller shaft of the vehicle and which causes the brake holder to function to hold the brakes at or about the time that theyehicle is brought to a stop or shortly after thevehicle is stopped, the time of application of the brake holder being manually variable to suit the driver of the vehicle and the time delay provided by the time-delay means being to'some extent automatically variable depending on .the rate at which the propeller shaft isdeoelerated.

speedometer shaft the storage battery-.34 of the motor vehicle. switch 28, time-delay means 39, and voltage con The control system is shown in one form in Fig. 3. It includes a switch 23 for closing the energizing circuit of the brake-holder solenoid 25; a -release switch .729, actuated iby the accelerator 4 being .closed when the accelerator .'.is released and in engine-idling position and opened in'all other positions; a time-delay means 39, and a voltage control or current-limiting means, which includes a choke coil arrangement 31 together with a switching means 32 adapted to be driven iroinpropeller shaft H, as for example from the Energy is derived from The trolmeans, except for the switching means 32, may conveniently be mounted in one suitable case (not shown). The switch means 32 may be mounted in a case 36, shown in Fig. l as located in backof the-speedometer.-;3lrof the veh-icle. The shaft 33-is contained in thebusual flexible-sheath, indicated at 38, and driven from propellershaft H in theusual manner .(not shown). The .release. switch t2fi'is, mounted adjacent the accelerator.

The control switch 28 includes a stationary member 39, which is-of insulatingmaterialuand from which one contact 40 of therswitch is adjustably Sup orted, and a-second and inovable member it i which is also of insulating i materialanzl to which the other vcontactJl-Z of.the switch and a terminal clip- I-Sare suitablyfixed. The movable member 4i is fixed tonne. end .of .aleaf spring, 4 3, the other end-of which, together with rigid metallic bracket 65,.is suitably .fixed', to the first member 39. The clip..43 is connected by a jumper-wire 36 ,to spring .44. The-movable member ll .has fixed to itspthQrendarigid bracket 43. Thetime delaymeans 3!) consists of a resistance .wire, which interconnects the brackets 45 and ll and issuitably fixed at .its ends, one .toeach. This wire .30 normally.controlsthemovement of memberm tl .by the-spring i t in the direction which tends toengagethe contacts .62 and 4B, and vthus close switch .28. When .wirej3il is. heateditelongates and allows spring lid to .move. the contacts .40 and 4-2 into engagement. When wire. 35 cools it. moves member 4| against theiorce of spring .44.,to .disengagethese .contactsand openswitch 1128. ,The switch contact .49, as herein. shown,.is fixed ,to one endof a leaf spring .48,.the other-end of which, together with aterminalclip .50, are suitablyfixedto member 39. .A screw 5!, threaded into member .39, bears against spring .49 and, when turned, causes. the. contact ,40. to move .to- Ward or. away. from contact .42, .whereby thejdistancev betweenthecontactsmay be variedvtovary the timerequiredto engage vthecontacts. .The screw 5| maybe held inits variouspositions of adjustment inany suitable way, as forexample, byaspringili. engaging theihead of the .screw.

The switches .28, 29 and solenoid '26 arejin eluded in series in an energizing circuitithat'includeslthe battery 34, a manual switch,.53, which may be the usualignition switch, and .a fusef54. This circuit maybe traoedflas follows, 'from ,the ungrounded side of ,battery3 l,bya wire 55, closed ignition. switch 153,, a wire, 56,, fuse'.5,4, .a wirejl, spring 4'3, wire ,46, ,clip .'43,. engaged contacts 42 and 40, spring 49, clip 50, a wire 58, coil,2. 'i,,a wire-.59, and release switch ZSlto. the ground and thu tothe otherterminal of battery.,34.

The. voitageecontrol means includes. a coke .co'il having two equal-sections-tfl=and fil, mounted ona .magnetizable core (i2. 'lfhejunction of, these sections is connected by a .wire 63 to the time delay means 30. The other terminal of coil section 60 is connected tothe switching means 32. Such means includes spring contact fingers 65 and 61 respectively connected by wires G l andv 66'to the other terminals of coil sections 60 and GI and a pivoted switch member 68 for alternately engaging'the free ends of the contact fingers B5 and 61. The other end of member 68 is connected by a wire 69 to the ground and thus to the grounded side of battery 34. The switch arm 68 is drawn by a spring into engagement with a cam I l, which is fixed to the speedometer shaft 33. As shown, this cam has six lobes and thus the switch arm 68- will be oscillated six times during each revolution of shaft.33. The

shaft of a standard speedometer turns 1000 revolutions per mile. 'Hence, at a vehicle speed of say three miles per hour, shaft 33 will turn at 50 revolutions per minute and the switch arm 68 will be oscillated 300 times per minute at the described low vehicle speed. Thisswitch arm is arranged to move into engagement with, and then, by continued movement, flex each spring contact finger. It is also arranged to engage one spring contact finger before it disengages from the other trated has been previously flexed'downwardly, will move upwardly, as-switch arm 68 swings upwardly until the latter engages spring contact finger 65. Continued upward movement of arm 68 will flex finger B5 upwardly and cause it to disengage from spring contact finger 61. The arrangement is such that one finger or the other is always connected to switch arm 68. Thus, one section 60 or the other section-6l of the choke coil is always connected (whenever the ignition switch 53 is closed) in a circuit which includes battery 34 and the resistance wire 30.

' When the circuit is closed to one section of the choke coil, a current flow is established but, due to the inductance of the coil, there is a lag in building up current and time is required for the current to reach its maximum value. As the speed of the cam H increases, the time interval, during which a circuit to either section of the choke coil is closed, decreases and the maximum values to which the current can build up decrease. section of the choke coil in one direction and then through the other section of the choke coil in the opposite direction and a pulsating direct current wave is produced.

The choke coil and breaker arrangement constitute a means for varying the voltage applied to the time-delay means 30. One illustrative example of the resultobtained is shown in the graph 12 of Fig. 4, which shows voltage at the output wire 63' plotted against propeller shaft speed in revolutions per minute and also against vehicle speed in miles per hour (assuming no slippage of the driving wheels). Maximum voltage is obtained when the propeller shaft is stopped and both choke coil sections 60 and SI are connected to the battery at the same time and in parallel. This maximum may be, for example 3.5 volts. connected, the maximum value will be somewhat less, say for example 3 volts. As the propeller shaft I l speeds up, an initially very rapid decrease in voltageis secured, the voltage dropping to say 1.5 volts,.when a car speed of 5 miles perhour is attained, and thereafter, the decrease is at a: The voltages below 1.5 volts.

Thus the finger 61, which as illus- A current flow is built up through one When only one choke coil section is effective to actuate the time-delayineans sum;

ciently to clost switch 28.

The switching means 32, diagrammatically shown in Fig. 3, may, for example, be constructed" as disclosed in copending application Serial No. 211,512, filed February 17, 1951.

In the particular illustrative example shownherein, each ofthe choke coils .60 and BI con-- efficient expansion. These values are not critical and may be varied considerably. The set of values given merely illustrates one set that has been found suitable forthe purpose and, since there are many other values that are suitable, it is not desired to limit the invention to the one set, herein disclosed.

It has been found desirable in order to effect asmooth release of the brakes to shunt across the accelerator switch 29 a ballast resistor havinga resistance, which is low when the resistor is cold and which rises rapidly when the resistor be comes hot. One resistor, suitable for the pur-- pose, is a 3 C. P., 6-8 volt automotive type lamp 17. One terminal of this lamp is connected by a wire 78 to wire 59 and the other terminal of the lamp is connected by a wire 19 to the ground. When the switch 29 is closed, lamp "H is shunted out and full current fiows through the coil 26.- When switch 23 opens, the lamp is placed in series with coil 26 and by its resistance decreases the current flowing through coil 26.- 'The resist ance of the lamp, when cold, is relatively low but it increases rapidly, as the filament becomesheated, soon reaching a value such that the cur-' rent through coil 26 is decreased sufliciently to allow valve 22 to open. The arrangement effects a gradual reduction in current flow in coil 26= and thus a gradual reduction of the force op-- posing spring 21 so that the valve 22 opens gradually, thus avoiding the sudden opening of the valve and resulting sudden release of the brakes;

that would otherwise occur. v

In the operation ofdecelerating the vehicle-,- the operator will release the accelerator 4, allowing the latter to move to engine-idling position and the accelerator switch 29 to close. Pressure on pedal I6 will cause thebrakes'to be appliedand the vehicle to be deceleratedat a rate vary-{ ing with the degree of hydraulic pressure empioyed. While the energizing circuit of the wire 305 is closed at all times, when the ignition switch' 53 is closed, the voltage available, at relatively high propeller shaft speeds, say those corre-" spond'ng to vehicle speeds above 5 miles per. hour, are of insignificant value and are not ef-' fective, regardless of the length of time of ap-i plication, to cause enough current to fiow'l through this wire 30 to materially heat the same i and cause engagement of the contacts-of switch: Effective values of applied voltage, com-:- mence when the propeller shaft speed decreases; to a predetermined low value, say for example," that correspond'ng to a vehiclespeed of 5 miles 1 per hour. As the propeller shaft speed decreases. below the last-named speed, the voltage applied to wire 30 rises rapidly, as shown by graph 72 of Fig. 4, resulting in rapidly rising current, which anemic 7. GQIItfiCt'iD. Engagement of these iCOIltQlOl'iS-iCIDSGS the energizing circuit to the hrak-ezholdergsolenoid 25. flhe latter vcloses :valve :22 against the force ofispring 1.2! aanditrapsrbrakefluid in the brake cylinders ,of :the .:front wheels.

The extent of the time .delaywistmanuallyuvariable ,by adjustment ;of lth'ezspacing rof the contacts 4,0 and 42;as-by means aof screw .51. .This enables :adjustment of the "control to suit the driving .chabits 10f -:different roperators. 'Then :also, the :extent :of the timeldelay will vary to.-:some extentwwith the rate of deceleration becauseof variation in voltage :applied .to wire 30. For example, :if :the -:driver --sho.uld-:app1y the zbrakes suddenly and dock the :wheels, the maximum efiective voltage -,of ,315 volts would the ii-mmediately available and less time would be :required to @heat wire 38 -to the necessary-degree than :if the driver should decelerate @at .a normal rate, whenqthe voltage-would vary from the minimum tothe cma-ximum effective values :and the average voltage would be less, wherebyrslightlymore time would be required to heat the wire it for thepurpo-se. Also if the win this cold, *asat starting .or,-for-other;reasons to appeanthe contacts A0 and 4.2 are more widely separated ;and more time is required to move them together, sayabout two seconds. Under normal operating conditions the time-delay- .is about one and onehalf-iseconds.

'Ihe time of application --.of the brake holder depends on-the rate of deceleration of the propeller shaft. The :brake holder will be applied in 'a certain time after the propeller shaft has decreased to a relatively low speed, say, foraexthe braking pressure and .avoidthelurching stop that results, when the brake holder .closes before :the vehicle stops andbraking fluid .under relatively high pressure .is trapped in the brake cylinders. If .the deceleration is effected at .a rate slower than :normal, the brake holder will be applied before the propeller shaft stops-but, since relatively low braking pressure is .used, trapping er fluid .in the brake cylinders by the closing of the brake holder valve will ,not adversely alfect the smoothness of the stop. If the driver should coast to a stop, the brake holder may'be applied at a propeller shaft speed corresponding to a vehicle speed of about 2 milesv perhourbut there will be no braking pressure available until the driver presses on *the :brake pedal Hi. :In'general, a'quick stop'results 'in'a quick application of the brake "holder and a slow stop results in' a slow application of the brake holder. A .driver, who is ,in the habit of decelerating his car at high-rates, 'will 'wish'ithe control adjusted for" a shorter time delay than the driver who customarily decelerateshis car at a slower'rate.

Thequse"otthebrake holder on the front wheelscnly affords desirable anti-:s'kidprotection. If the driver applies his brakes to lock the wheels, "while 'they'are 'on icej'the brake holder "willbe 'appli'ed ina "few seconds but it willrnothold i-brakin :pressure .linathe rear wheels,

so @that the driver can release 3 his brakelin I order to pull-the :car .out of .a: skid, :allowing the; rear wheels to turn and, asesoon {as they :reach cbhe release speed the brakeeholder valve will open. However, the delay. afforded by the time-delay means, afternthe-brakeslock the wheels, is normally:.sufiicient for the operator to take the necessary action without the necessity of 1 thelrear wheelshaving to return to the-releasespeed.

'The inventionithusaaffords .-,a zbrake -holder control that is based on a-very simpleformlof timedelayvmeans, the effective action .of which is initiated, when the propeller shaft :of the vehicle reaches a certain low speed, .-and the extentof which may be approximately :the time neededto deceleratesuch shaft .at .a normal rate from the aboveementioned low speed to zero. lfhe =control;may, for example, be adjusted so that the brake holder will be ,appliedat .zero, .pr.op'eller shaft speed, whendeceleration is ate normal rate-.ofisayfrom 8 to .10 feetppersecond-persec- 0nd. Then if a high rate of -.deceleration, .say for "example 18 feet .per second per second, .is usedover the entire period of deceleration, the brake holder will not beapplied until .after the propeller shaft has .stopped. However, ,if the high rate -,is used initially, and .later the braking pressure 'is rrelaxed, .the brake .holder can be applied atzero speed.

The invention affords a time-delay type .of brake .holder .control that is applicable to .any type of automobile. The control is extremely simple and .is adapted for .quantity production .at lowunit costtand .is readily adjustable to .suit the wishes of differentidrivers.

What is claimed is:

A hr alre control zineans t for wheeled vehicles, core. rising, -a brake :holder, ielectricalmeans lior actuating the :brake .holder, :an energizing circuitfor .said #means adapted .for connection ,to asource of electricity, *2. switch in said ,circuit, a member having :a. relatively high .coeilicient of expansion-tor controlling the actuation .-.of .said switch respectively closing and "opening the same I by its expansion and contraction, :a :normally closed heating circuit .forsaid member adapted for connectionlto. .a source of electricity, voltage-varying :means in said heating circuit ,and including a rotatable .actuator ..adapted for .connection to the propellershaft of the vehicleand to be .ciriven by and atspeeds proportional to the speeds of such shaft, said voltage-varyingmeans varying the voltage .in the heating .circuitdnversel-y with the speed :of its .actuator and Iini- 'tiatingeffective heating .of .said .member .at a

predetermined low speed, corresponding to a low vehicle speed of only a .few miles an hourfto cause said member to be heated sufli'cien'tto actuate said switch and maintaining 'said member effectively heated 'at'all speeds below said predetermined speed. I

:2. Brake control means for wheeled vehicles, comprising, a brake holder, electrical means for actuating thebrake holder, an energizing circuit for saidmeansadaptedfor connection to .a source of electricity, v.a starting-switch insaid circuit, la-

when 'theresistor is relativelycool and operablewhen expanded to a predetermined extent to allow said resilient means to close the starting switch, a circuit including said resistor and adapted for connection to a source of electricity, and voltage-varying means in the last-named circuit and including a rotatable actuator adapted for connection to the propeller shaft of the vehicle and to be driven by and at speeds proportional to the speeds of such shaft, said voltagevarying means varying the voltage applied to said resistor inversely with the speed of said actuator and operable to reduce such voltage to values inefiective to heat said resistor suficiently to expand to said extent except at or below a predetermined l o w speed of said actuator corresponding to a vehicle speed of a few miles per hour.

3. Brake control means for wheeled vehicles, comprising, a brake holder, electrical means for actuating the brake holder, an energizing circuit for said means adapted for connection to a source or electricity, a starting switch in said circuit, a release switch in said circuit and adapted to be respectively closed and opened when the vehicle is decelerated and accelerated, resilient means tending to close the starting switch, a resistance wire holding said starting switch open 10 against the force or said resilient means and operable by elongation to a predetermined extent when heated to allow the starting switch to be closed by said resilient means, a normally closed circuit including said wire and adapted for connection to a source of electricity, and voltage varying means in the last-named circuit and including a rotatable actuator adapted for connection to the propeller shaft of the vehicle and to be driven by and at speeds proportional to the speeds of such shaft, said voltage-varying means varying the voltage applied to said wire inversely with the speed of said actuator and operable to reduce such voltage to values ineffective to heat said wire sufiiciently to elongate to said extent except at or below a predetermined low speed oi said actuator corresponding to a vehicle speed of a few miles per hour.

GLEN A. GUERNSEY. ARTHUR H. GREEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,187,789 Lanz Jan. 23, 1940 2,502,118 Ashton et a1 Mar. 28, 1950 

